In the use of a material handling system, it is desirable to provide means for automatically aligning a lifting element relative to material to be handled in order to substantially overcome problems associated with incorrect engagement of the lifting element and the material.
For example, a work vehicle, such as a lift truck, commonly has forks used to engage and lift material to be moved to another location. The lift truck has a manually operated valve to control the vertical movement of the forks. The operator of the lift truck adjusts the elevation of the forks in order to engage the material.
The material is frequently positioned on a pallet for convenient movement and storage. Proper alignment of the forks within the pallet opening is necessary to engage the load. The operator can sometimes misjudge the elevation of the forks and improperly engage the material. The result is damage to or tipping of the material from the pallet or movement of the pallet relative to the lift truck preventing engagement. This represents a waste of time and labor.
In automated material handling, the shuttle mechanisms used to retrieve and store materials generally require large operating clearances of the forks relative to pallet openings than is normally available. This can sometimes prevent use of the automated system with pallets and represents another waste of time and labor.
Therefore, it is desirable to provide means for delivering signals in response to preselected positions of the lifting element relative to the material to be loaded and adjacent structure and means for automatically moving the lifting element in response to receiving said signals for properly aligning the lifting element.